Actor Bruce Willis’ family has announced the diagnosis of a rare form of a neurodegenerative condition that has now brought an end to his acting career.

The 67-year-old Die Hard actor’s family wrote on Instagram Wednesday that Willis, has been diagnosed with aphasia, a language disorder caused by brain damage, and he would be “stepping away” from acting.

Aphasia is a language disorder—not necessarily a speech disorder—that affects about 1 million people in the U.S. with 180,000 diagnosed each year.

According to Kathryn Borio, a speech-language pathologist Aphasia impacts all language modalities [like] listening, reading, speaking, and writing. A hallmark symptom is this sort of ‘tip of the tongue’ phenomenon where I know the word but can’t find it.

Aphasia is mostly caused by a stroke affecting areas in the brain that control speech and language. This sort of damage to the brain impacts an individual’s ability to retrieve words or organize their words into sentences. In rarer instances, brain damage can be caused by a neurodegenerative condition that progressively worsens over time.